<template>
  <div>
    <router-link
      tag="div"
      to="/"
      class="header-abs"
      v-show="showAbs">
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showAbs"
      :style="opacityStyle"
    >
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>

<script>
import { onActivated, onDeactivated, reactive, toRefs } from 'vue'
export default {
  name: 'DetailHeader',
  setup(){
    const state = reactive({
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    })
    // methods
    const handleScroll = () => {
      const top = document.documentElement.scrollTop
      if (top > 50) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        state.opacityStyle = { opacity }
        state.showAbs = false
      } else {
        state.showAbs = true
      }
    }
    // activated
    onActivated(()=>{
      window.addEventListener('scroll', handleScroll)
    })
    // deactivated
    onDeactivated(()=>{
      window.removeEventListener('scroll', handleScroll)
    })
    return {
      ...toRefs(state)
    }
  }
}
</script>

<style lang="scss" scoped>
    @import '~@/assets/scss/main.scss';
  .header-abs{
    position: absolute;
    left: .2rem;
    top: .2rem;
    width: .8rem;
    height: .8rem;
    line-height: .8rem;
    border-radius: .4rem;
    text-align: center;
    background: rgba(0, 0, 0, .8);
    .header-abs-back{
      color: #fff;
      font-size: .4rem;
    }
  }
  .header-fixed{
    z-index: 2;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: $headerHeight;
    line-height: $headerHeight;
    text-align: center;
    color: #fff;
    background: $bgColor;
    font-size: .32rem;
    .header-fixed-back{
      position: absolute;
      top: 0;
      left: 0;
      width: .64rem;
      text-align: center;
      font-size: .4rem;
      color: #fff;
    }
  }
</style>
